The study included 2,919 people over 65 who had elevated homocysteine levels. Higher homocysteine is seen in people with dementia. Certain B vitamins, including the ones tested here, have been shown to lower homocysteine. The thinking was if you could lower homocysteine, you could reduce risk for dementia. B12 plus folic acid weren’t any better than placebo in this study, even though they did lower homocysteine:

“This study provides Class I evidence that 2-year supplementation with folic acid and vitamin B12 in hyperhomocysteinemic elderly people does not affect cognitive performance.”

People absorb less vitamin B12 as they age. Some develop outright deficiencies. It doesn’t matter whether they eat a lot of meat or are strict vegetarians. I wrote about that in The Case For Taking A Vitamin B12 Supplement. The people in this study were taking a lot of B12 – 500 micrograms a day (and 400 micrograms of folic acid). You only need about 2 or 3 micrograms a day. So, you can’t say they weren’t taking enough. You could say that cognitive function depends on other factors besides that one supplement.

B12 is needed for many processes. I’m still convinced it’s a good decision for older people to take it as a supplement and not rely on food. Even the government thinks so:

“Adults older than 50 years [should] obtain most of their vitamin B12 from vitamin supplements or fortified foods.”